1. Field of the Invention
The invention relates to above-ground swimming pools and comprehends maintaining the level of water in such swimming pools at the proper height.
2. Description of the Prior Art
Above-ground swimming pools are in common use. They are filled with water by special inlet conduits or simply by making use of a common garden hose to fill the pool initially and to replenish the water from time to time as the level drops owing to evaporation, splashing by occupants of the pool, and the like. It is generally convenient to maintain the level of the pool at the proper height by automatic means, but such automatic means as has previously been proposed has either been undesirably expensive or else subject to various defects. Apparatus within the pool is subject to damage by the rough action of the occupants of the pool and also occupies valuable space. Apparatus outside the pool, unless compact, also occupies valuable space. Some prior art devices require substantial modification of the existing pool wall or of the existing conduits, and the switching mechanism of some prior art devices tend to "hunt" or otherwise malfunction. Devices described in the prior art for maintaining the level of water in above-ground swimming pools include the following:
U.S. Pat. No. 3,908,206 to Crewing discloses a device which includes a water tank located adjacent the upper rim of an above-ground swimming pool. A body of water in this tank is connected by a pipe to a body of water in the swimming pool. This pipe extends from an aperture in the bottom of the tank to an aperture in the side of the swimming pool; it appears that this aperture in the side of the swimming pool must be specially provided. The function of this pipe is to equalize the water levels in the pool and in the tank. A water supply line connected to a float valve in the tank provides make-up water for the swimming pool when the water level in the pool falls below a predetermined height of the water level in the tank. The desired height is set by suitably elevating or lowering the tank in accordance with calibrated indicia.
The principal defect of this construction is the fact that the makeup water is supplied to the tank, the capacity of which is much smaller than that of the swimming pool. When the level in the swimming pool, and therefore the level in the tank, falls below a predetermined level, the float valve opens and water flows from the water supply line into the tank. However, if the water in the supply line is under the usual pressure, as is necessary if the pool is to be refilled reasonably promptly, the flow from the supply line will greatly exceed the flow which exits from the tank through the pipe. Consequently, the level of the water in the tank is restored to the proper height quickly, before any appreciable change has occurred in the level in the pool. As a result, the float valve is closed soon after it has been opened. As water continues to flow through the pipe as a result of gravity feed due to the difference of water levels as between the pool and the tank, the level in the tank will again fall to a level at which the float valve opens. Thus the float valve "hunts": it opens and closes frequently until the level in the pool is restored. This "hunting" action causes undue wear and tear on the float valve. The "hunting" action does not depend on the type of valve used, and would occur no matter what type of valve is used. Indeed, such "hunting" action would be even more deleterious in the case of a pressure-sensitive valve.
Moreover, even though the device of Grewing uses the same conduit (pipe) to sense the water level and to fill the pool, a special aperture must be provided in the swimming pool.
U.S. Pat. No. 4,185,333 to Ortega discloses a device which controls flow at a spa rather than the flow at a pool. As appears from FIG. 2 of this patent, dirt from the top goes through the entire flow-control device on the way to the filter, and the resulting obstruction of flow would render this device inoperable.
U.S. Pat. No. 4,373,220 to Selsted discloses a device which does not function while the system is operating, as is clear from the "Abstract".
U.S. Pat. No. 4,621,657 to St. Ledger discloses a device suitable for use in a big commercial pool, and it requires a lot of space. It is not suitable for an above-ground swimming pool; rather it is designed for an in-ground construction.
U.S. Pat. No. 4,972,530 to Synder discloses a device which is intended to be installed when the pool is constructed. The device is mounted inside the pool, and is therefore subject to damage by the occupants of the pool. Even the creation of waves in the pool can trigger undesired operation of the flow-control device.
U.S. Pat. Nos. 3,895,645; 4,065,095; 4,180,096; and 4,240,606 to Johnson disclose pressure-sensitive valves of a construction which, when properly modified, may be used as the pressure-sensitive valve of the present invention.